Fainting is when you lose consciousness or “pass out” for a short time, usually about 20 seconds to a minute. In medical terms, fainting is known as syncope.

Keep reading to learn more about the symptoms, what to do if you feel like you’re going to faint, and how to prevent this from happening.

Fainting usually happens when the amount of blood flow to your brain suddenly drops. This can happen for many reasons, some of which are preventable.

Symptoms of fainting, or feeling like you’re going to faint, usually come on suddenly. Symptoms may include:

If you’re prone to fainting or have a condition that makes you more likely to faint, there are steps you can take to help reduce your risk of passing out.

If you feel like you’re going to faint, some of the following steps may prevent you from losing consciousness:

  • If you can, lie down with your legs in the air.
  • If you can’t lie down, sit down and put your head between your knees.
  • Whether you’re sitting down or lying down, wait until you feel better and then stand up slowly.
  • Make a tight fist and tense your arms. This can help raise your blood pressure.
  • Cross your legs or press them together tightly to raise your blood pressure.
  • If you think your lightheadedness may be caused by a lack of food, eat something.
  • If you think the feeling may be caused by dehydration, slowly sip water.
  • Take slow, deep breaths.

If you see someone who looks as if they’re about to faint, have them follow these tips. If you can, bring them food or water, and get them to sit or lie down. You can also move objects away from them in case they do faint.

If someone near you faints, be sure to:

  • Keep them lying on their back.
  • Check their breathing.
  • Make sure they’re not injured.
  • Call for help if they’re injured, not breathing, or don’t wake up after 1 minute.

Fainting happens when the blood flow to your brain decreases, or when your body doesn’t react fast enough to changes in how much oxygen you need.

There are many potential underlying causes for this, including:

  • Not eating enough. This can cause low blood sugar, especially if you have diabetes.
  • Dehydration. Not taking in enough fluid can cause your blood pressure to drop.
  • Heart conditions. Heart problems, especially arrhythmia (an abnormal heartbeat) or a blood flow blockage can disrupt the flow of blood to your brain.
  • Strong emotions. Emotions such as fear, stress, or anger can affect the nerves that control your blood pressure.
  • Standing up too quickly. Getting up too quickly from a lying or sitting position can result in not enough blood getting to your brain.
  • Being in one position. Standing in the same place for too long can lead to blood pooling away from your brain.
  • Drugs or alcohol. Both drugs and alcohol can interfere with your brain chemistry and cause you to have a blackout.
  • Physical exertion. Overexerting yourself, especially in hot weather, can cause dehydration and a drop in blood pressure.
  • Severe pain. Severe pain can stimulate the vagus nerve and cause fainting.
  • Hyperventilation. Hyperventilation causes you to breathe very fast, which can prevent your brain from getting enough oxygen.
  • Blood pressure medications. Some blood pressure medications can lower your blood pressure more than you need.
  • Straining. In some cases, straining while urinating or having a bowel movement can cause fainting. Doctors believe that low blood pressure and a slow heart rate play a role in this type of fainting episode.

If you faint once and are in good health, you probably don’t need to go to the doctor. But there are some cases when you should definitely follow up with your doctor.

See your doctor if you:

  • have fainted more than once recently or often feel like you’re going to faint
  • are pregnant
  • have a known heart condition
  • have other unusual symptoms in addition to fainting

You should get medical care immediately after fainting if you have:

It’s also important to get immediate care if you faint and can’t be woken up for over a minute.

If you go to your doctor or urgent care after fainting, they’ll first take a medical history. Your doctor or healthcare provider will ask about your symptoms and how you felt before you fainted. They’ll also:

Depending on what your doctor finds in these tests, they may do other tests. This may include:

If you don’t have an underlying medical condition, fainting every now and then is usually nothing to worry about. However, if you have fainted more than once recently, are pregnant, or have heart issues, or other unusual symptoms, follow up with your doctor.

If you find yourself feeling faint, you can take steps to prevent passing out. The most important thing is to get your blood pressure back up and to ensure that your brain is getting enough blood and oxygen.

If you have conditions that make you more likely to faint, make sure you follow your doctor’s recommendations to reduce your risk of fainting.